Okay so this article, and the one it links back to, make much of the "rejected by veterinarians" line, but it's incredibly unclear as to why. Carbon dioxide would be an awful way to go, but I don't understand why, of someone is going to be killed (and not just killed but having their pattern erased when it could be preserved, known time of death in a controlled facility is a best case for cryo), nitrogen hypoxia is considered bad instead of a best option. Can someone explain this? As I understand it your get giddy and happy, then pass out, then die. Why is that unethical, if you've already decided the killing is ethical?